feat: add polygon mumbai testnet

hardhat.config.ts

@@ -34,6 +34,7 @@ const chainIds = {
   mainnet: 1,
   optimism: 10,
   "polygon-mainnet": 137,
+  "polygon-mumbai": 80001,
   rinkeby: 4,
 };
 
@@ -70,6 +71,7 @@ const config: HardhatUserConfig = {
       mainnet: process.env.ETHERSCAN_API_KEY,
       optimisticEthereum: process.env.OPTIMISM_API_KEY,
       polygon: process.env.POLYGONSCAN_API_KEY,
+      polygonMumbai: process.env.POLYGONSCAN_API_KEY,
       rinkeby: process.env.ETHERSCAN_API_KEY,
     },
   },
@@ -92,6 +94,7 @@ const config: HardhatUserConfig = {
     mainnet: getChainConfig("mainnet"),
     optimism: getChainConfig("optimism"),
     "polygon-mainnet": getChainConfig("polygon-mainnet"),
+    "polygon-mumbai": getChainConfig("polygon-mumbai"),
     rinkeby: getChainConfig("rinkeby"),
   },
   paths: {